public interface Stack<E> {
    //入栈（压栈）
    public void push(E e) throws Exception;

    //出栈
    public E pop() throws Exception;

    //查看栈顶元素
    public E peek() throws Exception;

    //查看栈内有多少元素
    public int getSize() throws Exception;

    //查看是否为空
    public boolean isEmpty() throws Exception;
}
